One Time Encounter/Breast Feeding Risk

Approx 2 weeks ago I (35 white male) had one time unprotected vaginal sex with my best friends gf (her 37 white, him 35 white).  He was participating as well but there was no male to male contact.  I am in a serious relationship and have only had two partners (including this one) in the past 36 to 48 months.  I recently had a child with my gf and we both tested negative for HIV 6 months ago.  My question, I did have sex with my girlfriend once about 24 - 48 hours after the unprotected vaginal sex with my friends fiancé and it occurred to me that I my have put my son at risk as he is 5 months old and breastfeeding.  So long story short, is there a risk that a child could get HIV from my gf via me from this type of exposure?

I did ask my friend about std's and was told they are clear but truth be told I didn't realize until after the fact that HIV could be spread thru breast feeding so I feel absolutely terrible that I may have put my son in jeopardy over a stupid one night "fling"  We are in the midwest united states (if that helps in terms of risk).  I will most certainly get tested at 6 weeks but the guilt and anxiety over the possibility of impacting my loved ones from my lack of judgement is devastating and starting to seriously affect my quality of life.  I also will not have sex with my gf until my test results come back.

[H. Hunter Handsfield, M.D.]

Welcome to the HIV forum.

It is difficult for me to imagine why you might be worried that your friend and/or his girlfriend might have HIV.  Are they injection drug users who are likely to share injection equipment?  Is he bisexual?  Is one of them an immigrant from an HIV-endemic country, like in Africa?  Has he been in prison, where he might have had sex with men (even if he isn't gay)?  Is she a commercial sex worker?  If none of those things, the chance either of them has HIV is extremely low.  And even with those risk factors, the chance you were infected from a single exposure is very low.  HIV is harder to transmit than you seem to think.  If a woman has HIV, the average transmission chance to a male parter is once for every 2,000 episodes of unprotected vaginal sex.  That's why it typically takes several years before HIV is transmitted among married couples having regular sex.

If I were in your situation, with the knowledge I have, I wouldn't even get tested for HIV -- unless, of course, your friend and his partner have one of the risk factors.  And I would not stop having unprotected sex with my wife.  But since you're worried about it, have an HIV test.  Even better, talk to your friend and tell him your fears -- and ask that he and his partner be tested.

Bottom line:  Probably there is no significant HIV risk, and no reason to be worried about infecting your son.  It isn't going to happen.

Regards--  HHH, MD